1. Field of the Invention
This invention relates to a non-auto crosslinking binder compositions containing poly(meth)acrylate resins in water dilutable lacquers which are preferably capable of being deposited electrophoretically, and to aqueous electrodip lacquer coating compounds [KTL baths (cathodic dip coating baths)] capable of being deposited at the cathode and their use for coating articles.
2. Description of the Related Art
Electrodip lacquer coating compounds are used on a large technical scale as primers. They are also referred to as electrophoresis lacquers or EC (electrocoating) lacquers.
Binders based on poly(meth)acrylate resin used for the formation of color stable lacquer coats of the kind required, for example, for the domestic appliances industry have not hitherto attained the level of protection against corrosion which has been achieved with amino epoxy resins in the motor car industry.
Thermal crosslinking of these systems is carried out by various processes, e.g. by reactions of functional groups in the basic resin with formaldehyde condensation resins, blocked polyisocyanates or transesterifiable crosslinking agents. Depending on the customers requirements, not all the wishes concerning the properties of the lacquer are fulfilled.
In DE-A No. 34 36 346 there are described aqueous, non-yellowing electrodip lacquer coating compounds containing, as basic resin, synthetic resin binders containing primary and/or secondary hydroxyl groups and primary, secondary and/or tertiary amino groups, such as amino-poly(meth)acrylate resins having a hydroxyl number of from 80 to 250 (mg KOH per g of solid resin), an amine number of from 30 to 150 (mg KOH per g of solid resin) and an average molecular weight (Mn) of from 250 to 10,000. This resin system has the disadvantage of not providing sufficient protection against corrosion, especially at the edges and corners of the coated articles.